The present invention relates generally to medical devices and methods. More particularly, the present invention relates to apparatus and methods for performing angioplasty, stent delivery, and related procedures using balloon catheters having ultrasonically oscillated surfaces which can impart energy to a blood vessel being treated.
Despite the growing sophistication of medical technology, vascular (blood vessel) diseases, such as acute myocardial infarction (heart attack) and peripheral arterial thrombosis (blood clots in leg arteries), remain a frequent, costly, and very serious problem in health care. Current methods of treatment, often expensive, are not always effective. In the U.S. alone, the cost of treatment and support and the loss of productivity due to vascular diseases together exceed $40 billion per year.
The core of the problem is that diseased sites within the blood vessels narrow and eventually become completely blocked as a result of the deposition of fatty materials, cellular debris, calcium, and/or blood clots, thereby blocking the vital flow of blood. Current treatments include drugs, interventional devices, and/or bypass surgery. High doses of thrombolytics (clot-dissolving drugs) are frequently used in an effort to dissolve the blood clots. Even with such aggressive therapy, thrombolytics fail to restore blood flow in the affected vessel in about 30% of patients. In addition, these drugs can also dissolve beneficial clots or injure healthy tissue causing potentially fatal bleeding complications.
While a variety of interventional devices are available, including angioplasty, atherectomy, and laser ablation catheters, the use of such devices to remove obstructing deposits may leave behind a wound that heals by forming a scar. The scar itself may eventually become a serious obstruction in the blood vessel (a process known as restenosis). Also, diseased blood vessels being treated with interventional devices sometimes develop vasoconstriction (elastic recoil), a process by which spasms or abrupt reclosures of the vessel occur, thereby restricting the flow of blood and necessitating further intervention. Approximately 40% of treated patients require additional treatment for restenosis resulting from scar formation occurring over a relatively long period, typically 4 to 12 months, while approximately 1-in-20 patients require treatment for vasoconstriction, which typically occurs from 4 to 72 hours after the initial treatment.
The use of ultrasonic energy has been proposed both to mechanically disrupt clot and to enhance the intravascular delivery of drugs to dissolve clot and inhibit restenosis.
Ultrasonic energy may be delivered intravascularly using specialized catheters having an ultrasonically vibrating surface at or near their distal ends.
It would be desirable to provide improved devices, systems, and methods, for treating vascular diseases, particularly stenotic diseases which occlude the coronary and other arteries. In particular, it would be desirable to provide methods and devices for enhancing the performance of angioplasty procedures, where the ability to introduce an angioplasty catheter through a wholly or partly obstructed blood vessel lumen can be improved. Moreover, it would be desirable to provide mechanisms as part of an angioplasty catheter, which mechanisms can assist in initial balloon deployment and/or decrease the likelihood of subsequent clot formation and restenosis. The devices, systems, and methods, should further be useful with other procedures which employ balloon catheters, including stent deployment and drug delivery, where drug delivery can be achieved by deploying a pair of spaced-apart balloons for defining a treatment region therebetween.